1. Field of the Invention
The present invention relates to a Packet Switched Data Network (PSDN) having a Local Area Network (LAN) interface and an overload control method thereof.
2. Description of the Related Art
A Packet Switched Data Network (PSDN) is generally required for data communication. Such a PSDN is a type of communication network for data transmission operated by a public telephone company, and comprises at least one Local Area Network (LAN) interface for connection to an external subscriber terminal having a LAN interface, and a main controller for processing packet data transmitted/received from the external subscriber terminal via the LAN interface and an Internet Control Message Protocol (ICMP) as well.
The PDSN delivers sound information using a Voice over IP (VOIP) as well as a data communication between external terminals. The VoIP is a term referring to IP telephone technology for a series of equipment for transmitting sound information using an Internet Protocol (IP).
In a PSDN, a single main controller controls at least one LAN interface for maintenance and an Internet phone call, and a physical layer and data link layer thereof are realized in a LAN dedicated chip.
A conventional PSDN is operated such that the LAN interface thereof generates an interrupt routine and the main controller then controls a protocol for processing packet data to transmit/receive packet data or to process ICMP.
In such a PSDN, if heavy traffic congestion occurs in any LAN interface, an overload is generated in the main controller for controlling packet data processing and Internet phone so that the whole system may become inoperable.
Such heavy traffic congestion can also occur by hacking or viruses and so on.
The majority of hacking has been conducted against servers, but the object of the hacking has recently tended to change from servers to communication equipment. Also, viruses causing heavy traffic have increased.
However, if traffic congestion occurs in one LAN interface among one or more LAN interfaces, the conventional PSDN manages, because of the execution of an interrupt routine, the main controller of the corresponding LAN interface, which processes packet data, is overloaded by processing packet data congested in certain LAN interface, thereby hardly processing inherent functions of the other LAN interfaces and a main processor.
Accordingly, due to the processing of congested packet data, the main controller of the conventional PSDN has drawbacks in that the PSDN may operate abnormally, or the entire PSDN can become inoperable.
Furthermore, since the conventional PSDN provides “Unreachable destination” for a traffic or broadcast message for a closed port, an anti-hacking measure further has a bad effect on system stability.
Although some of LAN dedicated chips have a complementary function for MAC instrumentation, there is a problem in application thereof because a communication system by nature has to respond or not respond after receiving a message from externally accessed communication equipment.